Corrosion inhibited trichloroacetates



CORROSION 1 u-nrnn TRICHLOROACETATES No Drawing. Application August 29, 1952, Serial No. 307,166

13 Claims. (Cl. 260-539) This invention relates to new compositions of trichloroacetates which have improved non-corrosive properties when in contact with the surface of metals, and to methods of minimizing the corrosive action of trichloroacetates on metallic surfaces. In particular this invention relates to new compositions of the water-soluble salts of trichloroacetic acid and inorganic phosphates, which compositions have improved non-corrosive properties when in contact with the surface of metals.

Salts of trichloroacetic acid which are soluble in water have found wide ranges of uses in the arts as weed killers, as agents for breaking petroleum water-in-oil type emulsions, such as are commonly found or obtained from producing oil wells or from the bottoms of oil storage tanks, and as catalysts for intermediates in certain chemical reactions. in the practical employment of trichloroacetates in these applications, the trichloroacetate of necessity comes in contact with metallic surfaces both before and after use, causing corrosion and rapid deterioration of such surfaces thereby making the use of these compounds objectionable. For example, tank cars, drums, storage tanks, spraying equipment, metal reactors, piping and the like are all caused to corrode by rusting and pitting when in contact with both the aqueous solutions of the water-soluble trichloroacetates and with such trichloroacetates in powder form.

it is therefore an object of the present invention to render the trichloroacetates substantially less corrosive to metals by adding to them a corrosion inhibitor which materially decreases the corrosive effects of the trichloroacetate. It is another object to provide such corrosion inhibitors which do not adversely affect the color of the rcsultant composition. Still another object is to provide such compositions which do not cause additional precipitation of sludges beyond that encountered in the absence of the inhibitor. A further object is to make available compositions of the water-soluble salts of trichloroacetic acid containing corrosion inhibitors which minimize attack on metals due to pitting and etching and which minimize loss of weight of the metal.

We have found that these and related objectives are accomplished by the present invention which comprises minimizing the corrosion of metals by the water-soluble salts of trichloroacetic acid, by dispersing therein watersoluble inorganic phosphates whereby an improved trichloroacetate composition is produced which when in contact with metals, causes only a fraction of the corrosion which results when using the trichloroacetate alone, and does not impart objectionable color or sludge to the trichloroacetate, all as more fully described hereinafter.

Among the compounds which we have found to be most effective for the purpose of this invention are the watersoluble inorganic phosphates, especially the alkali metal phosphates including the ammonium, sodium and potassium phosphates. More particularly, we have found phosphates selected from the group consisting of phosphoric acid, alkali metal and ammonium salts of phosphate, monohydrogenphosphate, dihydrogenphosphate, metaphosphate, hexametaphosphate, pyrophosphate, and mixtux-es thereof, especially useful.

tts ate 2,740,813 Patented Apr. 3, 1956 l ce num, copper, brass and those of the ferrous group especially mild steel.

In addition galvanized metals and tin plated metals may also be protected.

Satisfactory results are obtained in accordance with this invention by incorporating into the trichloroacetate to be corrosion inhibited more than 0.1 and up to 1.5 percent on the dry weight basis of the corrosion inhibitor. More than 1.5 percent may be used but little additional inhibition is observed even after extended exposure. Optimum results are realized in the corrosion inhibition of aqueous solutions of an alkali metal or ammonium trichloroacetate such as sodium trichloroacetate by incorporating therein 0.3 to 1.0 percent of a phosphate selected from the group consisting of phosphoric acid, alkali metal and ammonium salts of phosphate, monohydrogenphosphate, dihydrogenphosphate, metaphosphate, hexametaphosphate, pyrophosphate and mixtures thereof.

We have found that by keeping the solution alkaline in which the phosphates have been dispersed, better retardation of corrosion in the metals is obtained. By adding a common alkali such as sodium hydroxide or sodium carbonate to adjust the solution to a pH of between 7.5 and 10.5, the range between 8.0 and 9.0 being preferred, superior results are obtained.

In order to produce the corrosion inhibited compositions of this invention the phosphates can be incorporated into the trichloroacetates by mere mechanical mixing.

The following examples are given to illustrate preferred embodiments of our invention and they are not to be construed as limiting except as defined in the appended claims. In all runs, except where indicated, technical grade sodium trichloroacetate (designated herein as STCA) commonly available in commercial quantities was used and was made up to 45 percent by weight concentration with distilled water. All runs were conducted at room temperatures of approximately twenty-four degrees centigrade. Some of the runs were made using stagnant unaerated solutions while others were aerated. In those which were aerated, the air was bubbled in at a uniform rate; this provided agitation as well. v Chimneys were placed over the bubbling tubes to prevent air from impinging on the specimens.

Solids precipitated out on the bottom in all runs and were measured as volume percent after centrifuging 15 minutes at about 650 R. P. M. in a centrifuge whose rotational circle diameter was 18 inches.

The solution pH was adjusted to between 7.5 and 10. with alkali as measured with a Beckman Model G pH meter.

All specimens were hung in the solutions above the bottom but totally submerged in the liquid. The method of preparing the specimens was the same in each case: Metal pieces 3.0 inches by 1.0 inch by 0.05 inch were cleaned with number emery cloth and sapolio soap. They were then cleaned with alcohol, dried in the oven, weighed, and placed in the solutions to be tested. Upon removal from the corroding solutions, the specimens were washed with soap and water. If this did not remove the scale, they were made cathodic in an electrolytic cell using a current density of -20 amperes per square decimeter in an electrolyte of an inhibited solution of five percent by volume sulfuric acid. If this failed, they were scraped gently with a piece of magnesium and returned to the cell. This process was repeateduntil the specimens were cleaned. They were washed with alcohol, dried in the oven and then weighed. The corrosion rate is reported as milligrams per square decimeter per day" ting/sq. dm./day). Percentages of inhibitors used are given on a solid STCA basis.

Example I .--Mi'la' steelAerated-One percent inhibitor concentration when used Example 5. -Admiralty bras-Unaerated-Tlzrec-tenths percent inhibitor concentration Corrosion pg Inhibitor m j Remarks dmJday) 39'. 0.2% Solids. Blank 333i 133: 4.2. 6 Do. 4 Do.

Purified Blank 2i). Do.

7 l6. 9 0.5% Solids. Phosphoric Acid (HAPO) 13 g 3g; 17. 1 D0.

8. 4 20.0% Solids. 9. 1 Do. Phosphoric Acid with 0.6% 8 9 Do 00.01:. 3

15. 1 0.4% Solids. Sodium Monobaslc Phosphate 3g (NaHzPOyHzO) 2 8 0.7%DS olids. w .0 0. Sodium Dibasic Phosphate (NllzHPOrTHzO). 3 5g;

8 0.2%DSolids. 4 0. Sodium 'lribusic Phosphate Nairoi-izmo). 5% 3: 20. 5 7 Do. Sodium liexamctaphosphatmu. g 15. 3 Do.

17. 2 0.3% Solids. Sodium Metnpliosphste 8 8g: 19. 0 Do. 27.2 2.5% Solids. Sodium Pyrophosphate g3: 26. 3 Do. }Banox 4 32. 6 7.8% Solids. Banox A g3: 39. 2 Do.

"When adding a chemical equivalent of calcium chloride to the HaPOl there is apparently a. considerable increase in corrosion inhibition, however, there was a great increase in solids which precipitated out giving undesirable sludge and color to the solution.

*Banox 4 and Bones A are the trade names for a mixture of alkali metal phosphate glass sold by Oalgon, Incorporated, Pittsburgh, Pennsylvania having 9. Nero to P205 ratio between 1.1 to 1 and 1.2 to 1.

Example 2.-Mild steel-Unaerated-One-half percen inhibitor concentration 1 Example 4.Aluminum-Unaerated--0ne percent inhibitor concentration Corrosion Run N o. Inhibitor figyg Remarks dmJday) 47. 0 Deep isolated pits. Blank 29. 9 Do. Phosphoric Acid-.-- fig B3:

Corrosion Run No. Inhibitor Rate, mg./

' sq. din/day 56 Blank 1. 5 57 Banox 1..." 1.0

inhibitor concentration Corrosion Rate. mg] sq. dmJdsy Run No. 'Inhibitor Blank 34. Banox 4"...

A solid composition which is inhibited against corrosion by metals comprising a water-soluble salt of trichloroacetic acid and sulficient water-soluble inorganic phosphate to act as a corrosion inhibitor therefor was prepared on a commercial plant scale by a neutralizing a solution of trichloroacciic acid with sodium hydroxide, and adding to the resultant sodium trichloroacctate solution, about 0.7 percent of a sodium phosphate asa corrosion inhibitor in the form of the commercial material sold under the trade name of Banox 4 by Calgon, Incorporated, Pittsburgh, Pennsylvania. The composition produced was then dried in a vacuum drier and the soil composition compris ing sodium trichloroacctate and the phosphate inhibitor was packed and shipped in commerce with the realization of improved resistance to corrosion when in contact with metals.

The water-soluble inorganic alkaiies which may be employed inorder to adjust the pH of the solution are the common alkalies such as sodium hydroxide, sodium carbonate, potassium hydroxide, etc. whereby new compositions, comprising: a Water-soluble salt of trichloroacetlc acid, a water-soluble inorganic phosphate, as a corrosion inhibitor therefor, and, a water-soluble inorganic alkali,

-may be produced in accordance with this invention.

Among the water-soluble salts of trichloroacetic acid which are embraced within the scope of this invention are the alkali metal salts such as sodium trichloroacetate, potassium trichloroacetate, and including ammonium trichloroacctate, alkyl-radical-containing salts of trichloroacetic acid, ctc.; it is to be understood that although sodium trichloroacctate was employed in the above examples for the purpose of illustrating certain detailed embodiments of'this invention, we do not contemplate being limited thereto except as defined in the appended claims.

We claim: 1. A composition of matter comprising a water-soluble salt of trichloroacctic acid and as a corrosion inhibitor therefor, a water-soluble inorganic phosphate selected from the group consisting of phosphoric acid, alkali metals and ammonium salts of hexarnetaphosphatc, monohydrogenphosphate, dihydrogenphosphate, phosphate, pyrophosphate, mctaphosphatc, and mixtures thereof, in an amount greater than 0.1 per cent by. weight of the trichloroacetate.v

2. A composition of claim 1 wherein the phosphate comprises 0.3 to 1.0 percent by weight of the trichloroacetate.

3. A composition of claim 1 wherein the water-soluble tricholoracetate is an alkali trichloroacetate.

4. A composition of claim 1 wherein the water-soluble trichloroacetate is sodium trichloroacetate.

S. A composition of claim 1 wherein the corrosion inhibitor is phosphoric acid.

6. A composition of claim 1 wherein the corrosion inhibitor is sodium monobasic phosphate.

7. A composition of claim 1 wherein the corrosion inhibitor is sodium hexametaphosphate.

8. A composition of claim 1 wherein the corrosion inhibitor is sodium metaphosphate.

9. A composition of claim 1 wherein the corrosion in hibitor is sodium pyrophosphate.

10. A composition comprising a water-soluble salt of trichloroacetic acid, a water-soluble inorganic phosphate selected from the group consisting of phosphoric acid, alkali metals and ammonium salts of hexametaphosphate, monohydrogenphosphate, dihydrogenphosphate, phosphate, pyrophosphate, metaphosphate, and mixtures thereof, as a corrosion inhibitor therefor in an amount greater than 0.1 per cent by weight of the trichloroacetate, and, a Water-soluble inorganic alkali.

11. A solid composition being inhibited against corrosion by metals comprising a water-soluble salt of trichloroacetic acid and a water-soluble inorganic phosphate selected from the group consisting of phosphoric acid, alkali metals and ammonium salts of hexametaphosphate, monohydrogenphosphate, dihydrogenphosphate, phosphate, pyrophosphate, metaphosphate, and mixtures thereof, in an amount greater than 0.1 per cent by weight of the trichloroacetate to act as a corrosion inhibitor therefor.

References Cited in the file of this patent UNITED STATES PATENTS Alquist et al May 29, 1951 OTHER REFERENCES Spitz: Chem. Abstracts, vol. 41, col. 3425 (1947). Uhlig: Chem. Abstracts, vol. 43, 001.1707 (1949). Pryor et al: Nature, vol. 167, p. 157 (1951). Magee: Chem. Abstracts, vol. 45, col. 6147 (1951). 

1. A COMPOSITION OF MATTER COMPRISING A WATER-SOLUBLE SALT OF TRICHLOROACETIC ACID AND AS A CORROSION INHIBITOR THEREFOR, A WATER-SOLUBLE INORGANIC PHOSPHATE SELECTED FROM THE GROUP CONSISTING OF PHOSPHORIC ACID, ALKALI METALS AND AMMONIUM SALTS OF HEXAMETAPHOSPHATE, MONOHYDROGENPHOSPHATE, DIHYDROGENPHOSPHATE, PHOSPHATE, PYROPHOSPHATE, METAPHOSPHATE, AND MIXTURES THEREOF, IN AN AMOUNT GREATER THAN 0.1 PER CENT BY WEIGHT OF THE TRICHLOROACETATE. 